Froome penalised for breaking rules banning feeding in the last 20km of the stage

There was French fever as Christophe Riblon won stage 18 of the Tour de France -- but it was Britain's Chris Froome who extended his overall lead despite being handed a penalty.

The famous Alpe d'Huez route asked more of the riders this year as, for the first time, the pack made a first ascent before descending back to the valley floor and then climbing the mountain for a second time.

After an attacking ride, Froome fell foul of the energy-sapping conditions inside the last five kilometers of the 172-km route.

The Briton sent his Sky team-mate Richie Porte back to the support car for food -- even though it is against the rules to 'feed' inside the last 20 kilometers of a stage.

Race officials handed Froome a 20-second penalty but the yellow jersey holder still stretched his lead over rival Alberto Contador to five minutes, 11 seconds.

"Richie was feeling a lot better than I was and I was running out of sugars towards the end," explained Froome, who is aiming to win his first Tour de France after helping Sir Bradley Wiggins to the crown last year.